Petrology and geochemistry of igneous rocks at Amphoe Bueng Sam Phan Changwat Chachoengsao

Abstract

This project is conducted to study the differences in geochemistry and petrography of igneous rock from Amphoe Bueng Sam Phan, Chawat Phetchabun and from Changwat Chachoengsao, aiming to imply to the differences in tectonic activities in the past between the two areas. Based on field investigation and petrological study, there are six types of igneous rocks collected from Bueng Sam Phan area, which are gabbro, diorite, granodiorite, basalt, basaltic andesite and andesite, while there is only one of igneous rocks collected from Chachoengsao area, which is granite.Major element characteristics indicate that the Bueng Sam Phan plutonic rocks have higher amount of Mg, Ti, Ca, Al and Fe than the Chachoengsao plutonic rocks but the Chachoengsao plutonic have higher amount of K than the Bueng Sam Phan plutonic rocks. They also suggest that the Bueng Sam Phan plutonic rocks derived from metaluminous and calc-alkaline magma series, which the trace element study suggests the volcanic arc tectonic environment. For the Chachoengsao plutonic rocks, they are suggested to have metaluminous to peralkaline and high K calc-alkaline to shoshonite magma source with the syn-collisional tectonic environment.